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Research supported by the Crew Endurance Team shows improved crewmember preference and individual performance compared with non-circadian schedules. The handbook outlines why crew endurance affects operational effectiveness, safety, morale, and long-term health, and provides guidance for selecting watch rotations, planning factors, constraints, and best practices.",{"@graph":63,"@context":119},[64,80,102],{"@type":65,"itemListElement":66},"BreadcrumbList",[67,71,74,77],{"item":68,"name":69,"@type":70,"position":9},"https://docshare.wps.com","Home","ListItem",{"item":72,"name":10,"@type":70,"position":73},"https://docshare.wps.com/template/",2,{"item":75,"name":46,"@type":70,"position":76},"https://docshare.wps.com/template/paper-templates/",3,{"item":78,"name":59,"@type":70,"position":79},"https://docshare.wps.com/template/crewendurance-handbook-a-guide-to-applying-circadian-based-watchbills/393002/",4,{"url":78,"name":59,"@type":81,"image":82,"author":87,"headline":59,"publisher":90,"fileFormat":93,"inLanguage":57,"description":61,"dateModified":94,"datePublished":95,"encodingFormat":93,"isAccessibleForFree":96,"interactionStatistic":97},"DigitalDocument",{"url":83,"@type":84,"width":85,"height":86},"https://docshare.wps.com/thumbnails/crewendurance-handbook-a-guide-to-applying-circadian-based-watchbills/393002.png","ImageObject",442,249,{"name":88,"@type":89},"Margaret","Person",{"url":68,"name":91,"@type":92},"DocShare","Organization","application/pdf","2026-10-09","2026-09-25",true,{"@type":98,"interactionType":99,"userInteractionCount":101},"InteractionCounter",{"@type":100},"ViewAction",7,{"@type":103,"mainEntity":104},"FAQPage",[105,111,115],{"name":106,"@type":107,"acceptedAnswer":108},"What is a circadian-based watchbill?","Question",{"text":109,"@type":110},"A circadian-based watchbill is a work and rest schedule that conforms to a 24-hour day, aligning watch, meals, and sleep to approximately the same times each day.","Answer",{"name":112,"@type":107,"acceptedAnswer":113},"Why does crew endurance matter operationally?",{"text":114,"@type":110},"Operational effectiveness depends on endurance: excessive fatigue threatens mission accomplishment, performance and safety, and it also harms morale and long-term physical and mental health.",{"name":116,"@type":107,"acceptedAnswer":117},"How does the handbook recommend improving sailors’ endurance?",{"text":118,"@type":110},"It emphasizes a circadian-based watchstanding schedule, focusing on alert watchstanders, understanding good sleep practices, using the 24-hour circadian rhythm, and building a stable daily schedule that maximizes rest opportunities.","https://schema.org",{"og:url":78,"og:type":121,"og:title":59,"og:site_name":91,"og:description":61},"article",{"robots":123,"canonical":78},"index,follow",{"doc_id":125,"site_id":56},393002,1791353992,{"code":4,"msg":5,"data":128},{"doc_id":125,"user_id":129,"nickname":88,"user_avatar":130,"doc_module":9,"category_id":45,"category_name":46,"doc_title":59,"doc_description":61,"doc_content":131,"file_id":132,"file_url":133,"file_type":134,"file_size":135,"view_count":101,"is_deleted":4,"is_public":9,"is_downloadable":9,"audit_status":9,"page_count":136,"language":137,"language_code":57,"site_id":56,"html_lang":57,"table_of_contents":138,"faqs":139,"seo_title":140,"seo_description":61,"update_tm":141,"read_time":142},137451207643,"https://ap-avatar.wpscdn.com/davatar_3d24733baf745e90a7e4bdd5f77d97b2","C R E W E N D U R A N C E H A N D B O O K  \nA Guide to Applying Circadian-Based Watchbills  \nCONTENTS  \nExecutive Summary 1  \nWhat is Crew Endurance? 2  \nWhy Crew Endurance Matters 2  \nHow to Increase Sailors’ Endurance 4  \nPlanning Factors 5  \nConstraints 5  \nChoosing the Right Watchbill 6  \nBest Practices 8  \nWorst Practices 9  \nTemplates for the Circadian Watch Rotations 10  \nThe 3/9 Circadian Watch Rotation 12  \nThe 6/18 Circadian Watch Rotation 14  \nThe 4/8 Circadian Watch Rotation 16  \nThe D5/N3 Circadian Watch Rotation 18  \nOur Vision 20  \nEXECUTIVE SUMMARY  \nA circadian-based watchbill is the term used for a work and rest schedule that conforms to a 24-hour day, allowing individuals to work, eat, and sleep at approximately the sametime each day. When you combine the number of hours spent on watch with the number of hours off watch (whether doing other work, eating or sleeping), a circadian-based system will add up to 24 hours. The system aligns with the naturally-occurring 24-hour rhythm which drives all biological processes, down to the cellular level.  \nResearch conducted by the Crew Endurance Team at the Naval Postgraduate School over the past several years has  \ndemonstrated how circadian-based watchbills are superior to non-circadian watchbills in terms of crewmember preference and individual Sailor performance.  \nThis handbook is being provided to commanders and their staff to share some of the valuable lessons learned through scientific investigation and trial and error by other Naval commanders. It is not meant to be prescriptive but gives examples of some past watchbills that have been used effectively.  \nFor more information or to provide feedback, please visit the Crew Endurance website.  \n[nps.edu/crewendurance](nps.edu/crewendurance)  \nNaval Postgraduate School  \nWHAT IS CREW ENDURANCE?  \nThe ability to maintain optimal warfighting performance while enduring job-related physical, psychological, and environmental challenges.  \nWHY CREW ENDURANCE MATTERS  \nOperational effectiveness depends on crew endurance. If crewmembers are overly fatigued, mission accomplishment, performance and safety are in jeopardy. Morale suffers. Chronic sleep debt has long-term physical and mental health consequences and degrades human performance.  \nSleep is a Weapon.  \nA Clear Mind is a Combat Edge. Fatigue Increases Operational Risk.  \nThe figures shown on the following page come from the Fatigue Avoidance Scheduling Tool (FAST). They represent predicted effectiveness over a 12-week period for an individual Sailor on two different watchbills, the 3/9 and the 5/10 . The figures illustrate how a Sailor performs when rotating through all watch sections while receiving 7 hours of sleep each day.  \nThe GREEN horizontal band represents 90% and above predicted effectiveness; the YELLOW band is the cautionary zone and represents 65 to 90% predicted effectiveness; the RED band is the danger zone and represents 65% and below predicted effectiveness.  \nDuring waking hours for an individual who is getting adequate sleep, predicted effectiveness should remain in the green band, dipping into the yellow zone during sleep periods. Blood Alcohol Equivalence is shown on the right axis.  \nFATIGUE AVOIDANCE SCHEDULING TOOL (FAST)  \n  E ectiveness (%)     E ectiveness (%)    \nSection 1 Section 2 Section 3 Section 4  \n3/9 Watch Rotation-Rotating Every 3 Weeks (better performance)  \n100- -0  \n90- 80-  \n70-  \n- .05 - .08  \n60-  \n50-  \n Time (12 weeks)   \n5/10 Watch Rotation (poorer performance, consistently dipping into the red)  \n100- 90- 80-  \n70-  \n-0  \n- .05  \n- .08  \n60-  \n50-  \n Time (12 weeks)   \nBlood Alcohol Equivalence (%) Blood Alcohol Equivalence (%)  \n Work (black) / Sleep (blue)  \n Predicted E ectiveness (>90%)  \n Cautionary Zone (65-90%)  \n Danger Zone (\u003C65%)  \nHOW TO INCREASE SAILORS’ ENDURANCE  \nOne method with proven results is the Circadian-Based Watchstanding Schedule. Numerous shipboard studies have shown how a circadian watchbill ","cbCais9JDSKMp0it","https://ap.wps.com/l/cbCais9JDSKMp0it","pdf",1819860,24,"English","# Executive Summary\n# What is Crew Endurance?\n# Why Crew Endurance Matters\n# How to Increase Sailors’ Endurance\n## Planning Factors\n## Constraints to Consider\n# Choosing the Right Watchbills","[{\"question\":\"What is a circadian-based watchbill?\",\"answer\":\"A circadian-based watchbill is a work and rest schedule that conforms to a 24-hour day, aligning watch, meals, and sleep to approximately the same times each day.\"},{\"question\":\"Why does crew endurance matter operationally?\",\"answer\":\"Operational effectiveness depends on endurance: excessive fatigue threatens mission accomplishment, performance and safety, and it also harms morale and long-term physical and mental health.\"},{\"question\":\"How does the handbook recommend improving sailors’ endurance?\",\"answer\":\"It emphasizes a circadian-based watchstanding schedule, focusing on alert watchstanders, understanding good sleep practices, using the 24-hour circadian rhythm, and building a stable daily schedule that maximizes rest opportunities.\"}]","CREWENDURANCE HANDBOOK - A Guide to Applying Circadian-Based Watchbills | PDF",1790376748,8]